package com.wnzt.baszh.util.common;

import java.io.FileInputStream;
import java.io.InputStream;
import java.security.MessageDigest;

public class MD5Util {
    /**
     * 生成MD5密文
     * 
     * @param s
     * @return
     */
    public static String MD5(String s) {
        char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                'a', 'b', 'c', 'd', 'e', 'f' };
        try {
            byte[] strTemp = s.getBytes();
            MessageDigest mdTemp = MessageDigest.getInstance("MD5");
            mdTemp.update(strTemp);
            byte[] md = mdTemp.digest();
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            return null;
        }
    }
    
    
    public static byte[] createChecksum(String filename) throws Exception {  
		   InputStream fis =  new FileInputStream(filename);          //<span style="color: rgb(51, 51, 51); font-family: arial; font-size: 13px; line-height: 20px;">将流类型字符串转换为String类型字符串</span>  
		  
		   byte[] buffer = new byte[1024];  
		   MessageDigest complete = MessageDigest.getInstance("MD5"); //如果想使用SHA-1或SHA-256，则传入SHA-1,SHA-256  
		   int numRead;  
		  
		   do {  
		       numRead = fis.read(buffer);    //从文件读到buffer，最多装满buffer  
		       if (numRead > 0) {  
		       complete.update(buffer, 0, numRead);  //用读到的字节进行MD5的计算，第二个参数是偏移量  
		       }  
		   } while (numRead != -1);  
		  
		   fis.close();  
		   return complete.digest();  
		}  
		  
		public static String getMD5Checksum(String filename) throws Exception {  
		   byte[] b = createChecksum(filename);  
		   String result = "";  
		  
		   for (int i=0; i < b.length; i++) {  
		       result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring(1);//加0x100是因为有的b[i]的十六进制只有1位  
		   }  
		   return result;  
		}
}

